Synthesis, characterization, and H/D exchange of μ-hydride-containing [FeFe]-hydrogenase subsite models formed by protonation reactions of (μ-TDT)Fe2(CO)4(PMe3)2 (TDT = SCH2SCH2S) with protic acids

Abstract

As [FeFe]-hydrogenase models, the first thiodithiolate (TDT) ligand-containing μ-hydride complexes [(μ-TDT)Fe₂(CO)₄(PMe₃)₂(μ-H)]⁺Y⁻ (2–7, Y = Cl, ClO₄, PF₆, BF₄, CF₃CO₂, CF₃SO₃) have been prepared by protonation reactions of (μ-TDT)Fe₂(CO)₄(PMe₃)₂ (1) with the corresponding HY acids. While the protonation reactions are monitored by in situ¹H and ³¹P{¹H} NMR spectroscopy to show the isomer type and stability of 2–7, the structures of the isolated 2–7 are characterized by elemental analysis, spectroscopy and for some of them by X-ray crystallography. Although the H/D exchange of μ-hydride complex 7 (Y = CF₃SO₃) with D₂ or D₂O has been proved not to occur under the studied conditions, the H/D exchange of 7 with DCl gives the μ-deuterium complex [(μ-TDT)Fe₂(CO)₄(PMe₃)₂(μ-D)]⁺[CF₃SO₃]⁻ (8) in a nearly quantitative yield. To our knowledge, 8 is the first crystallographically characterized μ-deuterium-containing butterfly [2Fe2S] complex produced by H/D exchange reaction.